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Chapter 1: Introduction

Anatomy is the science of the structure of the
body. When used without qualification, the term is applied usually to human anatomy.
The word is derived indirectly from the Greek anatome, a term built
from ana, meaning "up," and tome, meaning "a cutting" (compare the
words tome, microtome, and epitome). From an etymological point of
view, the term" dissection" (dis-, meaning" asunder, " and secare,
meaning "to cut") is the Latin equivalent of the Greek anatome.

Anatomy, wrote Vesalius in the preface to his De Fabrica (1543),
"should rightly be regarded as the firm foundation of the whole art of
medicine and its essential preliminary." Moreover, the study of anatomy
introduces the student to the greater part of medical terminology.

Anatomy "is to physiology as geography is to history" (Femel); that
is, it provides the setting for the events. Although the primary
concern of anatomy is with structure, structure and function should be
considered together. Moreover, by means of surface and radiological
anatomy, emphasis should be placed on the anatomy of the living body.
As Whitnall expressed it, "I cannot put before you too strongly the
value and interest of this rather neglected [surface] aspect of
anatomy. Many a student first realizes its importance only when brought
to the bedside or the operating table of his patient, when the first
thing he is faced with is the last and least he has considered." The
classical methods of physical examination of the body and the use of
some
of the various "-scopes," e.g., the stethoscope and the ophthalmoscope,
should
be included. Radiological studies facilitate achievement of "an
understanding of the fluid character of anatomy and physiology of the
living" (A.E. Barclay), and the importance of variation should be kept
in mind.

In relation to the size of the parts studied, anatomy is usually
divided into (1) macroscopic or gross anatomy, and (2) microscopic
anatomy or histology (now used synonymously). In addition, embryology
is the study of the embryo and the fetus, that is, the study of
prenatal development, whereas the study of congenital malformations is
known as teratology.

In general, works dealing with human anatomy are arranged either
(1) systemically,
that is, according to the various systems of the body (skeletal,
muscular,
digestive, etc.) or (2) regionally, that is, according to the natural,
main
subdivisions of the body (head and neck, upper limb, thorax, etc.). In
this
book, after the general features of certain systems have been discussed
in
introductory chapters, the remainder of the work will general follow a
regional
approach. The regional plan has been adopted chiefly because the vast
majority
of laboratory courses in human anatomy are based on regional
dissection.

Anatomical terminology

A discussion of etymology of many of the common terms used in anatomy is included in this online text. However, the following etymological works are recommended:

International agreement has been reached on an English and Latin
nomenclature, the Terminologia Anatomica. A revision of this
terminology is used in this book. Eponyms are avoided except where so
common in clinical practice as to be considered essential for the
medical student.

All descriptions in human anatomy are expressed in
relation
to the
anatomical position, a convention whereby the body is erect, with the
head, eyes, and toes directed forward and the upper limbs by the side
and held so that the palms of the hands face forward. There is no
implication that the anatomical position is one of rest. It is often
necessary, however, to describe the position of the viscera also in the
recumbent posture, because this is a posture
in which patients are frequently examined clinically.

The median plane is an imaginary vertical plane of section that
passes longitudinally through the body and divides it into right and
left halves. The median plane intersects the surface of the front and
back of the body at what are called the anterior and posterior me dian
lines. It is a common error, however, to refer to the" midline" when
the median plane is meant.

Any vertical plane through the body that is parallel with the
median plane
is called a sagittal plane. The sagittal planes are named after the
sagittal
suture of the skull, to which they are parallel. The term
"parasagittal" is
redundant: anything parallel with a sagittal plane is still sagittal.

Any vertical plane that intersects the median plane at a right
angle and
separates the body into anterior and posterior parts is termed a
coronal, or frontal, plane.

The term horizontal plane refers to a plane at a right angle to
both the
median and coronal planes: it separates the body into superior and
inferior parts. This is often termed an axial plane, particularly in
radiology.

The term transverse means at a right angle to the longitudinal axis
of a structure. Thus, a transverse section through an artery is not
necessarily horizontal. A transverse section through the hand is
horizontal, whereas a transverse section through the foot is coronal
(fig. 1-1).

The term medial means nearer to the median plane, and lateral means
farther from it. Thus, in the anatomical position, the thumb is lateral
to the little finger, whereas the big toe is medial to the little toe.
Intermediate means lying between two structures, one of which is medial
and the other lateral. In the upper limb radial means lateral and ulnar
means medial: in the lower limb fibular or peroneal means lateral and
tibial means medial. The border of a limb on which either the thumb or
the big toe is situated is sometimes called preaxial, and the opposite
border, postaxial. These two terms are based on the arrangement of the
limbs in the embryo during the sixth postovulatory week, when the
thumbs and the big toes are both on the rostral border of the limbs
(see figs. 8-10 and 15-11).

Medial and lateral rotation (which should never be referred to as
internal and external) means rotation (e.g., of the hip) around a
vertical axis so that the anterior aspect of the part moves medially or
laterally, respectively.

Anterior or ventral means nearer the front of the body. Posterior
or dorsal
means nearer the back. In the upper limb the term palmar (formerly
volar)
means anterior. In the foot, plantar means inferior, and the term
dorsal
is commonly used for superior in the foot.

Superior means nearer the top or upper end of the body. Inferior
means nearer the lower end. Cranial or cephalic is sometimes used in
stead of superior, and caudal instead of inferior. Rostral means nearer
the "front end," that is, the region of the nose and mouth. this is
superior in the most of the body althoug it represents the anterior
aspect of the head.

The suffix "-ad" is sometimes added to a positional term to
indicate the
idea of motion. Thus, cephalad means proceeding toward the head. Such
terms
are useful occasionally in describing growth processes, but their
application is best limited.

In the limbs, proximal and distal are used to indicate,
respectively, nearer to and farther from the root or attached end of
the limb. (Proximal and distal have a special meaning in the case of
the teeth.)

Internal and external mean, respectively, nearer to and farther
from the
center of an organ or a cavity. Superficial and deep mean,
respectively, nearer
to and farther from the surface of the body.

The term middle is used for a structure lying between two others
that are anterior and posterior, or superior and inferior, or internal
and external.

In addition to the technical terms of position and direction,
certain common expressions may be cautiously used in anatomical
descriptions: front, back, in front of, behind, forward, backward,
upper, lower, above, below, upward, downward, ascending, descending.
These terms are free of ambiguity only if they are used in reference to
the anatomical position. A number of other common terms, such as
"under," however, are generally best avoided. In this work we will use
technical terms of position and direction.

History of anatomy

Anatomy can be traced from the Greek period, B.C.,
and the
Roman
Empire, A.D., to Andreas Vesalius, who reformed the subject in his De
humani corporis fabrica ("On the Workings of the Human Body") in 1543.
Subsequent highlights include the discovery of the compound microscope
(1590), the founding of microscopic anatomy by Malpighi (seventeenth
century), the discovery of the circulation of the blood by Harvey
(1628), the establishment of modern embryology by Wolff (eighteenth
century), the gross classification of tissues by Bichat (1801), and
many notable advances during the nineteenth and twentieth centuries.

The best general introduction to the history of anatomy is Singer,
C., A Short History of Anatomy and Physiology from the Greeks to
Harvey, Dover, New York, 1957. Two other interesting works are
Saunders, J. B. de C. M., and O'Malley, C. D., The Illustrations from
the Works of Andreas Vesalius of Brussels, World Publishing Co.,
Cleveland, 1950; and O'Malley, C. D., and Saunders, J. B. de C. M.,
Leonardo da Vinci on the Human Body, Schuman, New York, 1952.

Anatomical literature

In addition to journals (such as Acta Anatomica,
American
Journal
of Anatomy,
Anatomy and Embryology, the Journal of Anatomy and Clinical Anatomy),
many
detailed books are available. Some useful works are cited below.

1-2 Horizontal and coronal planes could
pass
through both shoulder joints.

1-3 Which type of plane is transverse
to (a)
the little finger, (b) the big toe, and (c) the neck?

1-3 Planes transverse to the little
finger or neck would be horizontal. A plane transverse to the big toe
would be coronal.

1-4 How is the thigh moved into a
position of flexion, abduction, and lateral rotation?

1-4 In flexion, abduction, and lateral
rotation,
the thigh is moved forward and laterally and is rotated around a
longitudinal
axis so that its front surface moves laterally. To refer to this as
"external"
rotation is incorrect usage. It should be noted that, in the absence of
fractures
and dislocations, the position of the foot should indicate whether the
extended
limb is rotated (laterally or medially) at the hip.

1-5 Which is the most important book
ever written on anatomy and when was it published?

1-5 The Fabrica of Vesalius, published
in
Basel in 1543, is one of the most important scientific treatises ever
published.

1-6 Was the circulation of the blood
appreciated at the time of Vesalius?

1-6 The circulation of the blood was not
appreciated until nearly a century after Vesalius, when it was
discovered by Harvey (1628).

Figure legends

Figure 1-1
Diagram showing the chief terms of position and direction and the main
planes of reference in the body